Last year we discussed security "walled gardens" with a network engineer for Canadian cable provider Cogeco. The practice limits the Internet access of an infected customer -- only allowing access to ISP-hosted cleanup tutorials, patches and other resources. The practice lowers an ISP's call volume (as opposed to just cutting them off) while protecting other users on the network.

The Washington Post blog today touches on security walled gardens and focuses on Cox's use of the tactic, which began in 2005 and reaped significant rewards:

"Prior to initiating this program, Cox was taking roughly 22,000 customers offline each year for Trojan infections. By 2005, that number was down to 8,000. And in 2006, the first full year in which it had those mechanisms in place, it confined slightly more than 1,800 users out of a user base of more than 3.3 million."

The report suggests that other ISPs have been hesitant to employ the tactic because they don't care about spam, and (as the Cogeco engineer hinted) executives can't neatly monetize the impact of infected machines. Instead, many ISPs "beef up the strength of their network so they can just carry the bad traffic along with the good."